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Flashcards in Gap junctions/Electrical Synapses Deck (43)
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1
Q

What are gap junctions?

A

An array of intercellular channels for direct cell-to-cell communication.

2
Q

What are gap junctions composed of?

A

Connexins

3
Q

What type of current is used for cell-to-cell communication?

A

Ionic current

4
Q

What leads to complex assemblies of subunits of gap junctions made?

A

Co-expression of connexins.

5
Q

How are intercellular channels at gap junctions packaged?

A

Densely packed

6
Q

What direction is signalling between cells using gap junctions?

A

Bidirectional

7
Q

Give two examples were gap junctions are used?

A

Oocyte and granulosa cells.

Epithelial cells of the gut.

8
Q

What organ are gap junctions found in?

A

They are ubiquitous (found everywhere)

9
Q

Define “ubiquitous”?

A

Found throughout the body.

10
Q

What happens if there is a change in connexin protein or genes?

A

Causes connexin-associated disease.

Many of these as GJ are important throughout the body.

11
Q

What is the permeability of gap junctions?

A
They are permeable to:
 inorganic ions (K, Na, Cl, HCO3)
Small organic (signalling) molecules (cAMP, IP3)
Dyes
Metabolites (glucose)
12
Q

Describe the bystander effect that is mediated by the connexin?

A

When looking at tumorigenesis.
When intoxicating a cell with pro-drug it only kills that one cell while if gap junctions were used it kills off all bystander cells that has the toxic gene.

13
Q

What is the synaptic transmission mediated by?

A

Chemicals

14
Q

How many connexin genes are there?

A

20 different connexin genes

15
Q

Where are the connexin genes expressed? and by what type of cell?

A

Half are expressed in the brain.

Most by glia cells.

16
Q

What is the most important protein when looking at electrical synapses?

A

Cx36

17
Q

Name the two types of synapse transmission?

A

Chemical synapse.

Electrical synapse.

18
Q

What is the difference between chemical and electrical synapse?

A

Chemical: using a transmitter (no direct contact)
Electrical: without transmitter (direct contact to transfer tonic current)

19
Q

Assaying function of electrical synapses?

A

Specificity between different types.

Once applied cannot be reused

20
Q

Name the 3 characteristics of electrical synaptic transmission?

A

Can pass sub threshold current
Strongly postsynaptic responses
Bidirectional

21
Q

What is required for electrical transmission?

A

Ionic current

22
Q

Time difference between electrical and chemical transmission?

A

Electrical activate faster than chemical ones.

Synaptic delay

23
Q

Direction of release between electrical and chemical transmission?

A

Electrical almost always bidirectional.

Chemical not.

24
Q

Polarisation specificity between electrical and chemical transmission?

A

Chemical are de/hyperpolarising.

Electrical not specificity.

25
Q

Reliability between electrical and chemical transmission?

A

Electrical are reliable.

Chemical reliability varies.

26
Q

Metabolically expenditure between electrical and chemical transmission?

A

Chemical uses more energy than electrical.

27
Q

How would you test the electrical synapses?

A

Use gap junctions to look at the fast transmission between neurones.
Knockout the specific gene

28
Q

How would you test the chemical synapses?

A

Look at the morphology and protein associated with vesicle docking and release.

29
Q

Name the 6 properties that are important when looking at synapses?

A
  1. Bidirectionality.
  2. Shorter synaptic delay.
  3. Sign preservation.
  4. Mediated both hyper polarising and depolarising responses.
  5. Facilitates synchrony and promotes AP.
  6. Coordinates activity in cell-to-cell fashion.
30
Q

What kind of network is created by electrical synapses?

A

Synchronously coactive neurones.

31
Q

What does Cx36 do?

A

Creates multiple groups of coupled interneurones.
Restricted to interneurones.
Couples similar subtypes.
Creates homocellular assemblies.

32
Q

Name the two different expression of connexins?

A

Homomeric

Heteromeric

33
Q

Cx36 is vital for generating?

A

Synchrony generates brain rhythms

34
Q

What are electrical synapse vital for in the cerebellum?

A

Important in neural circuits.

35
Q

How are the inferior olivary nucleus important in motor impairment?

A

Neurones in this area generate sub threshold rhythms
Which occasionally trigger APs.
Send signals to the cerebellum.

36
Q

How are the Cx36 linked to the inferior olivary nucleus that is necessary for motor impairment?

A

The membrane rhythms in neurones of the olive are synchronised.
Requires electrical synapses. Thus requires Cx36

37
Q

Define “ataxia”?

A

When muscle contractions are impaired.

38
Q

What protein is most electrical synapses comprised of?

A

Cx36.

39
Q

What other things play a role in comprising the electrical synapses?

A

Other connexins and pannexins.

40
Q

What are the electrical synapses in the retina comprised of?

A

Other connexins.

41
Q

What passes through the electrical synapses?

A

Usually allows ionic current and small organic molecules.

Both directions.

42
Q

What is the role of the electrical and chemical synapses?

A

Together generate complex electrical activity that encodes brain function.

43
Q

Name 2 process that Cx36 is important in?

A

Brain retina and pancreas